The proposed study concerns the regulation of phosvitin messenger RNA synthesis by estrogenic hormones. The synthesis of phosvitin is initiated in the livers of male and female birds by estrogens. The initiation of the synthesis of the M-RNA for this phosphoprotein is presumably brought about through the participation of the estradiol-receptor complex present in liver nuclei. The initial aim of this study is to isolate, identify, and purify the M-RNA for phosvitin. The purified RNA will be used as template for the synthesis of complimentary DNA by the RNA instructed DNA polymerase of avian tumor viruses. The complimentary DNA will be used to study the kinetics of phosvitin M-RNA synthesis in rooster livers exposed to estrogens. Subsequent studies will be directed toward the role of the liver estradiol-receptor complex in the induction of this M-RNA.